docs: def run(self, options, args):
          """update install options with caching values"""
          if options.prune:
              previously_installed = pip_get_installed()
  
          index_urls = [options.index_url] + options.extra_index_urls
          with pipfaster_download_cacher(index_urls):
              requirement_set = super(FasterInstallCommand, self).run(
                  options, args,
              )
  
          required = requirement_set.requirements.values()
  
          # With extra_index_urls we don't know where the wheel is from
          if not options.extra_index_urls:
              cache_installed_wheels(options.index_url, requirement_set.successfully_downloaded)
  
          if not options.ignore_dependencies:
              # transitive requirements, previously installed, are also required
              # this has a side-effect of finding any missing / conflicting requirements
              required = trace_requirements(required)
  
              if not options.prune:
                  return requirement_set
  
              extraneous = (
                  reqnames(previously_installed) -
                  reqnames(required) -
                  # the stage1 bootstrap packages
                  reqnames(trace_requirements([install_req_from_line('venv-update')])) -
                  # See #186
                  frozenset(('pkg-resources',))
              )
  
              if extraneous:
                  extraneous = sorted(extraneous)
                  pip(('uninstall', '--yes') + tuple(extraneous))